1Department of Psychology, University of North Carolina, Chapel Hill, North Carolina 27599-3270, USA.

Abstract

BACKGROUND:

Drinking in the dark (DID) procedures have recently been developed to induce high levels of ethanol drinking in C57BL/6J mice, which result in blood ethanol concentrations (BECs) reaching levels that have measurable affects on physiology and/or behavior. The present experiments determined whether the increased ethanol drinking caused by DID procedures can be attenuated by pretreatment with CP-154,526; a corticotropin releasing factor type-1 (CRF1) receptor antagonist.

METHODS:

In Experiment 1, male C57BL/6J mice received ethanol (20% v/v) in place of water for 4 hours, beginning with 3 hours into the dark cycle. On the fourth day, mice were given an intraperitoneal injection of one of the 4 doses of CP-154,526 (0, 1, 3, 10 mg/kg) 30 minutes before receiving their ethanol bottle. In Experiment 2, C57BL/6J mice had 2 hours of access to the 20% ethanol solution, beginning with 3 hours into the dark cycle on days 1 to 3, and 4 hours of access to the ethanol bottle on day 4 of DID procedures. Mice were given an intraperitoneal injection of one of the 4 doses of CP-154,526 (0, 1, 3, 10 mg/kg) 30 minutes before receiving their ethanol bottle on day 4. Tail blood samples were collected immediately after the 4-hour ethanol access period on the fourth day of each experiment. Additional control experiments assessed the effects of CP-154,526 on 4-hour consumption of a 10% (w/v) sucrose solution and open-field locomotor activity.

RESULTS:

In Experiment 1, the vehicle-treated group consumed approximately 4.0 g/kg/4 h of ethanol and achieved BECs of approximately 30 mg%. Furthermore, pretreatment with the CRF1 receptor antagonist did not alter ethanol consumption. On the other hand, procedures used in Experiment 2 resulted in vehicle-treated mice consuming approximately 6.0 g/kg/4 h of ethanol with BECs of about 80 mg%. Additionally, the 10 mg/kg dose of CP-154,526 significantly reduced ethanol consumption and BECs to approximately 3.0 g/kg/4 h and 27 mg%, respectively, relative to vehicle-treated mice. Importantly, the 10 mg/kg dose of the CRF1R antagonist did not significantly alter 4-hour sucrose consumption or locomotor activity.

CONCLUSIONS:

These data indicate that CRF1R signaling modulates high, but not moderate, levels of ethanol drinking associated with DID procedures.

Consumption of 20% (v/v) ethanol (A) and blood ethanol concentrations (BECs) (B) following the 4-hour ethanol consumption test on day 4 of Experiment 1. Mice were given an intraperitoneal (i.p.) injection of the CRF1R antagonist CP-154,526 (0, 1, 3, 10 mg/kg) 30 minutes before access to ethanol. There were no significant differences between treatment groups. All values are means ± SEM.

Open-field locomotor activity (cm/h) during the 4-hour test following intraperitoneal (i.p.) injection of CP-154,526 (10 mg/kg) or the vehicle (Veh) 30 minutes before testing. There were no significant differences between the drug pretreatment groups at any time point. All values are means ± SEM.

Consumption of a 10% (w/v) sucrose solution following the 4-hour sucrose consumption test on day 4 of Experiment 4. Mice were given intraperitoneal (i.p.) injection of CP-154,526 (0, 10 mg/kg), 30 minutes before access to sucrose. There was no significant difference between the two groups. All values are means ± SEM.